Method of extracting potash and the like.



A.l B. ANDREWS. METHOD V0F EXTHACTING POTASH AND THE LIKE.

APPLICATION FILED IIIAI'I. e, me,

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Patented Mar., 4, 1919 AVI MMMMNNMMMWYPM@ @MMM a AAQI WSWS@ MAMA@ wm mww w IAI @mw m, mmml @@MMNMMJ @Mwmmmd @@Jwm@ Rwwmw I Uwwmwm VLM* ARTHUR. BURTON ANDREWS, 0F AUBURN, MAINE, ASSIG-NOR 0F ONE-HALF T0 HIMSELF .AND ONE-HALF TO HERBERT F. KELLEY, OF AUBURN, MAINE.

Specification of Letters Patent.

Patented Mar.- lll, 1919i..

Application led March 6, 1918. Serial No. 220,824.

To all 'whom 'it may concern.'

Be it known that I, ARTHUR B. ANnREws, a citizen of the United States, residing at Auburn, county .of Androscoggin, State of Maine, have invented certain new and useful Improvements in Methods of Extracting Potash and the like, of which the following is a specification.

This invention relates to the extraction of the alkaline content from silicates, especlally such. as feldspar, and particularly to the recovery of potassium in the form of potassium hydroxid by which a yieldls secured with a maximumof recovery of the potassium content, an'd with a minimum diiiculty as to those incidents of extraction which have been such serious factors in effecting a rapid and etlicient production.

My method is based 0n the old and well lmown digestion of feldspar w1th lime. In extraction by this process as in almost all other digestive processes, the two incidents of the process which make for expense in operation and limitation of output are the elements of time and pressure. Each of these factors as is obvious constitutes feaincidents of time and pressure be minimized as far as possible. It is probably sufficient to note that there has been considerable misapprehension as to the relation of these two collateral features of the digestive process.

It has been supposed by some that sustained cooking or increase of pressure or both would increase yield', while some have set up some delinite time or pressure as controlling the entire problem. I have found, however, that sustained cooking and increased pressure may easily be carried to a point where the process begins to reverse and rebuild the silicates. I also iind that the time'and the degree of pressure varies with different feldspars and must be determined by experiment for the individual circumstances of diiferent'feldspars and different methods. As will be more` clearly pointed out later on, both of these items are incident to the rates of digestive reaction, the completeness and rapidity and economy of the reaction being the important element of the method, and constituting the thing desired, while the time or pressure are incidental factors to be reduced as low as possible by the eiiiciency of the method.

My method consists, broadly speaking, of increasing the rapidity and \mpleteness of the reaction by dividing the ordinary digestive method into steps in accordance with principles which will be hereinafter explained, so that a maximum extraction of the caustic is effected with a minimum of material and at a substantial saving of time and pressure.

I have discovered that the rate of reaction in the digestive process between feldspar and the lime has a certain maximum phase bearing relation to the strength of the caustic solution as it is, in contact. In other words, the reaction proceeds more rapidly and more easily (thus involving less heat and pressure) up to a certain per cent. of caustic strength of solution, after which the rate of reaction falls olf rapidly, eventually reaching a point at which the reaction begins to reverse so that it is actually possible by digesting too long and at too high pressure to again break up the caustic and begin to reform it as a silicate.

My method therefore contemplates a division of the digestion into a fractional series vand an opposite progression in the fractional digestions so that-the liquor of maximum strength is brought into digestive relation with the material ofminimum potential reaction and vice versa. This fractional digestion in such a series increases the net rate of reaction at a considerable saving of time and will vdo soat comparatively low pressures. It furthermore byreason of its augmentive action builds up a than three may be employed, as conditions .'require. `Feldspar and caustic lime are introduced in-to a digester at one end of the lseries and to it is added the liquor from the next preceding digester, which liquor is we will say nearly completed 'and which has a minimum of reactive tendency and thus reuires the maximum tendency of the fresh c arge in order to raise -its strength.

The digester from which thls liquor comes isnfed with the sludge from the first-named digester which in the triple battery for exthe system it will be found voo 4able lterings and washings ample, would be the first digester. In this second or middle digester therefore, I combine thel sludge consisting of the partly decomposed 4and extracted material from the first digester with the Weak liquor from the third digester. This Weak liquor has still a considerable reactive potentiality which can lbe largely satisfied by even the partially extracted sludge from the first mentioned digester. The sludge from this second mentioned or middle digester is fed over toA a digester in which it is mixed with fresh water and to which is added such wash Water as is obtained in the final washing of any previous sludge after it has had its third reaction and before it is dumped out as the reject. This reject has had taken from it, according somewhat to the character of the materials used 95% to 98% of its alkaline content.

Tracing the course .of the liquor through (on the basis of a 10% K2O feldspar) that the water which has been digested with the 'sludge of two previous extractions will frequently be found to constitute a liquor of as high as one-half per cent. strength caustic potash. This liquor after digestion with the once digested sludge in the middle digester will be found to be augmented usually to about nine-tenths per cent. strength caustic potash, and the ultimate liquor from the digestion with the fresh material will be found to have a strength of about one and three-tenths per cent., which may then be economically evaporated in a-multiple effect evaporator, and finally dried in a fusion pan and packaged for shipment. The charge of each digester after cooking is separated by suitinto a sludge and a liquor. i

For convenience in visualizing my'method, I have illutrated in the single figure of the annexed drawing a graph descriptive of my method.

Various modifications may obviously be practised in the method and the results may vary somewhat with the eiiiciency of the apparatus and the skill and care employed in its operation. It may be stated, however, that I have been able to produce by my method as high as 98% extraction of potash from feldspar of about 10% KZO at average runs of six hours and employing only pressures of and 100 pounds. of lime required for` ordinary .operations is preferably of amount approximately double in weight to the amount of the feldspar. I also preferably supply the feldspar in very finely divided condition.

VWhat I therefore claim and desire to secure by Letters Patent is:

1. The process of'extracting alkali from The amount 'i silicates consisting 1n a progressive frac-` tional digestion with an alkaline earth metal hydrate by separating the liquor and sludge of each fractional digestion and adding the liquor of the most digested sludge to a less digestedsludge.

2. The process o f extracting alkali from silicates consisting in a series of progressive fractional digestions with an alkaline earth metal hydratel by establishing from successive digestions of successive charges a series of liquors of increasing strength and in successively digesting each digested charge with the liquor of the preceding digestion in the series.

3. The process of extracting alkali from silicates by digestion with an alkaline earth metal hydrate consisting in establishinga fractional digestive series in which the silicate and hydrate is introduced at the finishing end of the liquor and water is inios troduced at the opposite end yof the series,l

the liquor from the water end being progressed to digestive contact with each slud e and each sludge being progressed for said digestive contact with each liquor.

4. The process of extracting alkali from silicates by digestion with an alkaline earth metal hydrate consisting in establishing a series of simultaneous fractional digestions and in maintaining said fractional digestions by adding the augmented liquor of one digestion to the sludge from which` the next stronger batch of liquor was augmented.

5. The process of extracting alkali from silicates by digestion with an alkaline earthl metal hydrate consisting in establishing a series of simultaneous fractional digestions and in maintaining said fractional digestions by adding the augmented liquor of one digestion` to the sludge from whichv the next stronger batch of liquor was augmented, and

6. The process of making caustic potash In testimony whereof I aHix my signature from feldspar by digestion with lime conin presence of two Witnesses.

sisting in digestively treating each succes- ARTHUR BURTON ANDREWS. sive charge of feldspar and lime with the Witnesses:

5 liquor of a digestive treatment of the sludge EDITH M. DUNN,

of the preceding charge. CHAS. B. CARTEm Copies of this patent may be obtained Vfor ve cento eeoh, by acidi-easing the Commiasioner o Fatemtn,

mhiuton, D. G." s 

